Conventionally, as illustrated in FIG. 6, an electrophotographic printer capable of producing duplex copies and composite copies normally comprises the following: a transfer section 34 incorporating a photoreceptor 32 and a transfer charger 33, where an image is transferred to a sheet of copy paper S; a fixing section 36 having a pair of upper and lower heat rollers 36a, where the transferred image is fixed onto the copy paper sheet S; and a circulating path along which the copy paper sheet S carrying the image developed at the transfer section 34 and the fixing section 36 is reconveyed to the transfer section 34 to produce duplex copy or composite copy.
The transfer section 34, fixing section 36, and a transport belt 35 are arranged along the circulating path. The transport belt 35 conveys sheets of copy paper S from the transfer section 34 to the fixing section 36. As shown in FIG. 7, the path further has a diverter 37 for controlling the feeding direction of the copy paper S, a sheet inverting mechanism 40 for inverting the copy paper S, a sheet feeding apparatus 43 for reconveying the copy paper S to the transfer section 34, and plural rollers including transport rollers 38 for delivering the copy paper S.
As illustrated in FIG. 8, the sheet inverting mechanism 40 comprises a diverter 41 and a pair of inversion rollers 42. The inversion rollers 42 feed out a conveyed sheet of copy paper S in a direction opposite to the direction in which it has travelled. At this time, the diverter 41 turns in the A direction, so the copy paper sheet is fed out in the direction of the sheet feeding apparatus 43. This mechanism ensures that sheets of copy paper S are conveyed to the sheet feeding apparatus 43 in an inverted state.
As shown in FIG. 9, the sheet feeding apparatus 43 comprises an intermediate tray 44 whereon a stack of copy paper sheets S are temporarily stored, and an injection duct 45 for injecting air between the copy paper sheets S. The intermediate tray 44 is composed of a sheet stacker 44a where the copy paper sheets S are loaded, a suction duct 44b for pulling a copy sheet S' which lays at the bottom of the copy paper sheets S on the sheet stacker 44a, and a sheet feed belt 44c which delivers the bottom copy sheet S' in the E direction, i.e. to the transfer section 34. Sheets of copy paper S stored on the sheet stacker 44a are separated by the flow of air from the injection duct 45, and simultaneously the bottom copy sheet S' of the copy paper S is drawn down onto the sheet feed belt 44c by the suction duct 44b and conveyed to the transfer section 34.
In a conventional arrangement, however, the copy paper sheets S carrying an image which has been fixed thereto by the heat rollers 36a at the fixing section 36 tend to curl up due to great heat. Also, the diverter 37 coercively controls the feeding direction, so that the copy paper sheets S have curls corresponding to the curve of the diverter 37.
As illustrated in FIG. 9, this arrangement makes the copy paper sheets S loaded on the sheet stacker 44a in the sheet feeding apparatus 43 have downwardly curled edges. The down-curls form a space between the copy paper sheets S and the sheet stacker 44a in the middle. Therefore, when reconveying the bottom copy sheet S', the curls inhibits the air from the injection duct 45 from flowing. As a result, sheets can not be sufficiently separated, causing multi-feeds.